Review of solar thermal technologies in sustainable animal agriculture farms: Current and potential uses

At least 14.5% of the total greenhouse gas emissions significantly contributed from animal agriculture, emphasize the importance of more sustainable practices on farms. Solar thermal technologies offer a promising solution by providing clean energy for several key processes within animal agriculture, such as (1) drying animal feed, (2) drying animal products, and (3) heating processes. We comprehensively review the current and potential uses of solar thermal technologies for each of these processes, including the demand calculation and drying kinetics in the process. The pre-calculation phase of each process, including accurate demand calculations and the modeling of drying kinetics, is critical to optimizing the system’s performance. We also identify research gaps that need to be explored. For drying animal feed, most studies focus on food waste and are conducted in tropical regions. We show that there is significant potential to cut emissions further by applying solar thermal technologies to simply drying regular animal feed. Future research should examine technical and management challenges to make solar-powered drying a continuous process. Similarly, research on drying animal products mostly takes place in tropical countries, focusing on specified products like beef and fish. Expanding these studies to cover a wider range of products and incorporating additional preservation methods into drying kinetics calculations will help improve system sizing. Most solar heating research is based in Europe and often focus at hybrid systems that integrate solar thermal and photovoltaic (PV) technologies to meet electricity needs. There is a need for more studies on different heating applications, such as chicken brooders, and how hybrid PV systems can address continuous electricity demands. Additionally, more work is needed to evaluate the overall applicability of solar drying technologies in various regions and to establish standardized measures of emission reductions per kilogram of protein.